For many years, astragals have been provided on various types of closure members which move into and out of proximity to a fixed or a movable surface for effecting sealing engagement therewith. Examples of the types of applications for such astragels include the doors of garages, commercial and utility buildings, and similar applications. A wide variety of materials and geometric configurations have been employed in the construction of such astragels.
Originally, most doors of this type were manually operated, with large-sized or extremely heavy doors being counter-balanced to permit operation for opening and closing by a single person. The necessary usage of mechanical assistance in the instance of very large doors for commercial installations and more recently commonly in regard to smaller garage doors for the sake of convenience has resulted in the wide usage of electric motors to power the opening and closing of such doors. Attendant the usage of powered doors, there has arisen the safety concern of a power-operated door closing with a person or other foreign object in the opening. This has become a particularly troublesome consideration with the widespread usage of remote controllers to actuate the closing and opening of such doors from a distance or from an obstructed vantage point where it is impossible to ascertain that the door opening is free of obstructions or will necessarily remain free of obstructions during closing.
Generally two approaches have been taken to implement the safety feature of stopping or reversing such doors when an obstruction in the opening is encountered by the door during closing. In some instances, the motor or drive train effecting the closing and opening of the door is adapted to sense substantially increased displacement opposition exceeding that normally encountered during the closing of the door. While affording an extent of safety protection, these types of devices are often highly sensitive to precise adjustment, require frequent readjustment, and are otherwise prone to operational malfunction.
The other type of safety device for such doors contemplates the placement of some type of mechanical actuator, electrical switch, or sensor on the leading edge of the door to engage any object which might be encountered during closing of the door and actuate suitable controls to stop and/or reverse the motor which drives the door during opening and closing. Edge-mounted actuating devices have taken many forms. In some instances, bars of various types have been mounted on linkages and connected to a switch. In other instances, a cable member has been stretched between the extremities of the door edge which is adapted to actuate a switch when the cable is sufficiently displaced. Another approach has been to employ tubing of plastic or rubber which is flexible and filled with a liquid or gaseous pressure which is adapted to activate a switch when pressurized.
Efforts have also been made to develop an astragal which performs conventional sealing functions while incorporating the characteristics of a safety switch in an edge-mounted device. Such astragals commonly employ a base which is mounted to the door edge and a movable member which is positioned in spaced relation to the base. The base and the movable member mount substantially rigid or, in some instances, somewhat flexible conductive elements which are positioned in spaced relation during normal operation of a door. While offering some advantages with respect to mechanical linkage devices, these astragals have been subject to various types of problems resulting from the particular construction features employed. For example, past astragal construction configurations have precluded or made exceedingly difficult cutting an astragal to length at any time after manufacture. Also, depending upon the materials which may be employed, in some instances it is possible for moisture or dirt to permeate or enter the interior of the astragal and thus affect either the operability or reliability of the electrical contacts. In other instances, the movable member of the astragal, in carrying out its sealing function, may be permanently deformed to an extent that the electrical contacts are in permanent engagement, thereby rendering the safety-edge feature and the door inoperative. To counter this problem, the movable member may be constructed of a foam material, or foam may be interposed between the movable member and base for purposes of maintaining appropriate spacing between the electrical contacts. Different geometric configurations of the base and movable members of the astragal have also been tried to accommodate varying distortions in the movable member caused by irregular surfaces at which a seal is to be made, while providing consistent operation of an incorporated switching device; however, a reliable, inexpensive astragal providing the requisite sealing and safety features which is adaptable to different door profiles and useable on vertically-moving and pivotal doors has not emerged in the marketplace.